Rough idle

[93JC]

So, I replaced the spark plugs, plug wires, cap and rotor in my car last weekend. It has been idling erratically ever since. It almost feels like it's ~50 rpm too low, but I think it may be missing.

Is it fair to assume I buggered up at least one of the plug gaps?

[The Pirate]

It's a piece of shit, you should probably borrow Nick's flamethrower and torch that sucker.  Then, finally buy something.


Could be lots of things.  Is it just a rough idle (that wasn't there before)?  Car accelerates okay and has no drivability issues?  Double check your work.  And yeah, start with the plugs themselves.  I buy them pre-gapped, but almost always double check.  Had to made an adjustment once.

Is there a CEL?

I've actually never had to work on a distributor before.  Could that be the source of the problem?

[93JC]

It's a piece of shit, you should probably borrow Nick's flamethrower and torch that sucker.  Then, finally buy something.

Could be lots of things.  Is it just a rough idle (that wasn't there before)? Car accelerates okay and has no drivability issues?

Yup.

Double check your work.  And yeah, start with the plugs themselves.  I buy them pre-gapped, but almost always double check.  Had to made an adjustment once.

There is such a thing as pre-gapped spark plugs? I've never seen them pre-gapped. Bang-up fucking idea though.

Is there a CEL?

Nope.

I've actually never had to work on a distributor before.  Could that be the source of the problem?

Thought of that, in that the timing might be off. But I can't physically change the timing, it's still computer controlled. And it's not as though I installed the rotor incorrectly: it's keyed in with a screw.

[SVT32V]

So, I replaced the spark plugs, plug wires, cap and rotor in my car last weekend. It has been idling erratically ever since. It almost feels like it's ~50 rpm too low, but I think it may be missing.

Is it fair to assume I buggered up at least one of the plug gaps?

I suspect that you either knocked off/left off a vaccum line or have a bad wire.  Sometimes these new wires are not the highest quality especially the wire to electrode interface.

Try putting the old wires back on one at a time to see if you can rule that out.

This is a 4.0 liter EFI?

[93JC]

I suspect that you either knocked off/left off a vaccum line

This is what I originally thought. But I only disconnected one line in the process of replacing the plugs, and correctly reattached it.

However there was a rubber line attached to the air filter box which has gone missing. It was a short 90? elbow that didn't actually terminate anywhere, so I figured it's just a drain line to prevent the engine from sucking in water. Not that big a deal.



This is for my Spirit, so 3.0 L Mitsubishi V6.

[S204STi]

So, I replaced the spark plugs, plug wires, cap and rotor in my car last weekend. It has been idling erratically ever since. It almost feels like it's ~50 rpm too low, but I think it may be missing.

Is it fair to assume I buggered up at least one of the plug gaps?

Did replacing the rotor require removing the distributor?  If so I think you should check to see if you reinstalled it a tooth off.

[93JC]

No, all I had to do was take off the cap. I didn't yank the distributor shaft out.

[S204STi]

No, all I had to do was take off the cap. I didn't yank the distributor shaft out.

Did you use the correct spark plugs?

[93JC]

What do you mean 'correct'?! They looked like the old ones except they were clean. What more could you ask for?

[GoCougs]

What do you mean 'correct'?! They looked like the old ones except they were clean. What more could you ask for?

At a minimum, heat range and resistor vs. non-resistor.

[93JC]

I used the plugs the book in the parts store recommended.

[S204STi]

I used the plugs the book in the parts store recommended.

I once looked at a Yukon for such an issue and missed the fact that they have plugs that were about 1/8" too short, so basically the spark kernel was shrouded.  I think he got his plugs from a parts store too.

[FoMoJo]

Didn't mix up a couple of plug wires did you?

[Eye of the Tiger]

My Duster never had a rough idle. Maybe that's because of the Flowmaster. Best money I ever spent on that car.

[93JC]

The new plugs are exactly the same size as the old ones. No I didn't mess up the plug wires (I'd have much more trouble if I did).

We're not talking a huge problem here, it's just a slight shudder at idle every few seconds.

[JWC]

The new plugs are exactly the same size as the old ones. No I didn't mess up the plug wires (I'd have much more trouble if I did).

We're not talking a huge problem here, it's just a slight shudder at idle every few seconds.

You can't trust "pre-gapped" spark plugs.  Pull'em and recheck'em.   I've sold them and I've used them and every so often you get one with the gap too tight as if the plug was dropped.

[Eye of the Tiger]

You can't trust "pre-gapped" spark plugs.  Pull'em and recheck'em.   I've sold them and I've used them and every so often you get one with the gap too tight as if the plug was dropped.

A Flowmaster would be much more constructive than gapping the plugs.

[Secret Chimp]

I bought some AutoCrap wires for my Accord and it had an awful intermittent misfire, like stabbing the brakes on the highway. I had to return them.

[Eye of the Tiger]

I bought some AutoCrap wires for my Accord and it had an awful intermittent misfire, like stabbing the brakes on the highway. I had to return them.

I bet you didn't have a Flowmaster, either. Are you guys seeing the common denominator here? It's right in your faces.

[Rupert]

I've heard a lot of stories about bad plug leads...

Even with Flowmasters.

[Cookie Monster]

I've heard a lot of stories about bad plug leads...

Even with Flowmasters.

That's BS.

The Flowmasters replace the spark plugs.

[omicron]

We're not talking a huge problem here, it's just a slight shudder at idle every few seconds.

Even though it's not an Astron it thinks it is, and hence is shuddering its way into the pah-pah hall of fame.

[93JC]

Ha! I started yanking the plugs this morning and found the insulator on #4 was broken. I went back to the shop and exchanged it for a new one.

[93JC]

Booya! Problem solved.

[S204STi]

Booya! Problem solved.

GJ! 

[omicron]

Ha! I started yanking the plugs this morning

I'll bet you did.

[93JC]

Down, boy.